The present invention is directed to an abrasion resistant laminate for use as a covering for floors, countertops, table tops, store fixtures, etc.
It is well known that abrasion resistance particles can be applied on or within an overlay layer or on or within a decor sheet to enhance the abrasion resistance of the laminate. Examples of the techniques for applying these particles can be found in U.S. Pat. No. 3,798,111 to Lane, U.S. Pat. No. 5,141,799 to Mehta, and U.S. Pat. No. 4,713,138 to Ungar.
The use of polymeric substrates, particularly polyvinyl chloride, for covering floors and countertops also is well known. Many problems have been associated with this type of covering including the durability and wear surface characteristics of these products, as well as their limited aesthetic appeal. In an effort to increase the durability of these coverings, especially in high traffic areas such as department stores, office buildings, and shopping complexes, many consumers have resorted to the use of stone materials such as granite and marble. Although quite durable, these types of materials are very expensive and cost prohibitive to the average consumer.
An example of an abrasion resistant flooring product having an abrasion resistant or wear-resistant top layer laminate is currently being produced by Perstorp Flooring AB (Sweden) under the trademark PERGO(copyright). The PERGO(copyright) brand comprises a surface layer which provides strength and durability, a decorative layer which carries the design, and a base layer or substrate layer which provides strength, stability and heat resistance. The surface layer consists of cured melamine resin combined with cellulose paper and includes hard, abrasion resistant particles within or on the layer. The decorative layer consists of paper and melamine resin. The PERGO(copyright) product requires the surface layer and decorative layer to be laminated to a base or substrate layer which is based on a wood product. This wood-based substrate is typically particle board but could also include medium density fiberboard or hardboard. The strength and water resistance of this wood-based substrate is selected based upon the environment for which the flooring is used, e.g., standard domestic use, heavy domestic/moderate commercial use, or standard commercial use.
The use of a wood-based substrate in the PERGO(copyright) product and other similar types of laminates has many disadvantages associated therewith, the most important of these being that additional steps must be taken to provide some waterproofness to the wood-based substrate and to ensure that the product will only be exposed to limited amounts of moisture. Care must be taken when installing this product to ensure that sufficient adhesive is used between the planks to prevent water from penetrating into the wood-based substrate. Another disadvantage of these laminates is that, because they have a wood-based substrate, they are susceptible to environmental conditions and often expand and contract. Thus, they cannot be glued directly to a surface, such as a floor, and must be installed in a xe2x80x9cfloatingxe2x80x9d configuration. The installation of a xe2x80x9cfloatingxe2x80x9d floor requires the provision of a special tongue and groove configuration along the edges of the product to minimize shifting of the planks with respect to each other during and after installation. The glue is applied along these edges to hold the flooring planks in position on the floor. Another disadvantage of wood-based substrate flooring is that their installation typically requires the placement of a film vapor barrier layer of polyethylene and a foam layer of polyethylene to provide cushioning properties and to reduce noise upon one""s impact with the floor. The installation of these types of floors is very complex and often requires the services of a skilled professional, an expense that many consumers cannot afford.
FIGS. 1A-1C are cross-sectional views of various decorative products currently known in the prior art, as discussed above. The product shown in FIG. 1A comprises a polyvinyl chloride sheet 1. This sheet has limited aesthetical appeal and very little wear-resistance to scratching, scuffing, and/or tearing. The product shown in FIG. 1B comprises a laminate of a clear polyvinyl chloride top sheet 2, a polyvinyl chloride decorative sheet 3, and a polyvinyl chloride base sheet 1. While the FIG. 1B product provides a greater range of aesthetical options, the clear polyvinyl chloride top sheet 2 provides very little, if any, protection for this decorative sheet and often becomes scratched, scuffed, and/or stained. FIG. 1C shows a marble chip layer 4. While this product has excellent durability, it is very expensive and cost prohibitive to the average consumer.
The present invention provides an abrasion resistant laminate having a wear-resistant durable multi-layer surface assembly which is laminated to a base layer. The base layer is preferably formed from a polymeric substrate. The abrasion resistant laminate is aesthetically pleasing, sound absorbing, durable, wear-resistant, water-proof/water-repellant, stain resistant, less expensive to produce and easy to install. The laminate is also flexible and has reduced curl and warp. While the abrasion resistant laminate of the invention has particular utility in the manufacture of flooring, it may be useful wherever one desires a product having any or all of the abovementioned characteristics, such as for counter tops, table tops, store fixtures, wall coverings, etc.
The abrasion resistant product of the present invention comprises a durable wear-resistant top layer assembly comprising a wear resistant upper layer, a decorative layer, and a core layer. The wear resistant upper layer may be a separate overlay sheet having abrasion resistant particles on its surface or dispersed in the sheet itself. Alternatively, the wear resistant upper layer may be formed by coating the abrasive material directly on the decorative sheet or by dispersing the abrasive material into the decorative sheet. The technique of dispersing the abrasive material into the overlay or the decorative sheet occurs during the papermaking step of the overlay or decorative sheet. Known techniques may be used for applying the abrasion resistant particles.
The core layer comprises at least one, but preferably two or more layers of a material which provides reinforcement to the assembly. This core layer can include paper sheets, such as kraft paper sheets, which are typically impregnated with a resin, such as phenolic resin. The core layer can also include one or more additional layers formed from fiberglass, polypropylene, polyester, nylon, carbon fiber, or any known water resistant material. The additional layer may also be comprised of woven or nonwoven sheets and these sheets may or may not be impregnated with a resin, such as phenol . The use of the aforementioned additional layer reduces the expansion and contraction differential of the laminate, thereby providing dimensional stability and flexibility, as well as providing improved impact and anti-puncture characteristics.
Previously known laminates typically require impregnation of the decor sheet with a resin, usually melamine resin, in the amount of approximately 35-40 weight percent of the sheet. The preferred amount of impregnating resin in the invention is in the range of 0 to about 40 weight percent of the sheet, and is preferably not greater than about 30 weight percent of the sheet. The use of a reduced amount or no resin in the decor sheet produces a more stabilized laminate portion having reduced curl, reduced shrinkage, greater flexibility, greater strength, less brittleness and, therefore, less cracking.
A polymeric substrate is preferred for forming a base layer for the abrasion resistant laminate. This polymeric base layer is adhered to the bottom surface (or core layer bottom side) of the top layer assembly with a water resistant adhesive.
A thin balance layer is typically laminated onto the bottom surface of the substrate to provide balance, reduce curling and/or warping of the product, to help the product to conform to the floor surface, and to improve its sound deadening characteristics.
The wear-resistant top layer assembly may be applied to the substrate by two different preferred techniques. The first of these techniques is to form a high pressure laminate by stacking the layers of the wear-resistant top layer assembly and subjecting this assembly to heat and high pressure to cure and laminate the layers to one another. This high pressure laminate is subsequently adhered to the substrate base layer with the water resistant adhesive.
An alternative technique for forming this product is to use a low pressure method. The low pressure method can, in turn, be accomplished according to two different preferred techniques. The first of these techniques requires stacking all of the layers, those forming the wear-resistant top layer assembly, the water-resistant adhesive, and the base layer, and subjecting the stack to heat and low pressure to cure the layers and to laminate the layers together in a single step. The second technique requires initially laminating the layers of the wear-resistant top layer assembly under heat and low pressure and subsequently adhering this laminate to the base layer with the water resistant adhesive.
Further in accordance with the present invention, an abrasion resistant laminate comprises a substrate and a durable wear-resistant top layer assembly laminated over a top side of the substrate. The top layer assembly includes a wear-resistant upper layer and an underlying decorative layer which together include a first paper sheet impregnated with a first resin. The top layer assembly further includes a core layer underlying the decorative layer. The core layer includes second and third paper sheets impregnated with a second resin. A fourth paper sheet is interposed between the second and third paper sheets in the core layer. The fourth paper sheet is impregnated with the first resin, whereby the fourth paper sheet functions as a balance sheet to equalize expansion and contraction of the layers under the influence of environmental factors.